diff --git a/spring-core/src/test/java/org/springframework/core/io/buffer/DataBufferTests.java b/spring-core/src/test/java/org/springframework/core/io/buffer/DataBufferTests.java
index 45dc7e7a53..1739a47229 100644
--- a/spring-core/src/test/java/org/springframework/core/io/buffer/DataBufferTests.java
+++ b/spring-core/src/test/java/org/springframework/core/io/buffer/DataBufferTests.java
@@ -807,14 +807,14 @@ class DataBufferTests extends AbstractDataBufferAllocatingTests {
 
 		DataBuffer buffer2 = createDataBuffer(1);
 		buffer2.write(new byte[]{'a'});
-		split = buffer2.split(1);
+		DataBuffer split2 = buffer2.split(1);
 
-		assertThat(split.readPosition()).isEqualTo(0);
-		assertThat(split.writePosition()).isEqualTo(1);
-		assertThat(split.capacity()).isEqualTo(1);
-		assertThat(split.readableByteCount()).isEqualTo(1);
+		assertThat(split2.readPosition()).isEqualTo(0);
+		assertThat(split2.writePosition()).isEqualTo(1);
+		assertThat(split2.capacity()).isEqualTo(1);
+		assertThat(split2.readableByteCount()).isEqualTo(1);
 		bytes = new byte[1];
-		split.read(bytes);
+		split2.read(bytes);
 		assertThat(bytes).containsExactly('a');
 
 		assertThat(buffer2.readPosition()).isEqualTo(0);
@@ -822,7 +822,7 @@ class DataBufferTests extends AbstractDataBufferAllocatingTests {
 		assertThat(buffer2.capacity()).isEqualTo(0);
 		assertThat(buffer.readableByteCount()).isEqualTo(0);
 
-		release(buffer, buffer2);
+		release(buffer, buffer2, split, split2);
 	}
 
 	@ParameterizedDataBufferAllocatingTest
diff --git a/spring-core/src/testFixtures/java/org/springframework/core/testfixture/io/buffer/AbstractDataBufferAllocatingTests.java b/spring-core/src/testFixtures/java/org/springframework/core/testfixture/io/buffer/AbstractDataBufferAllocatingTests.java
index 47d18ffd66..2ad1a834a1 100644
--- a/spring-core/src/testFixtures/java/org/springframework/core/testfixture/io/buffer/AbstractDataBufferAllocatingTests.java
+++ b/spring-core/src/testFixtures/java/org/springframework/core/testfixture/io/buffer/AbstractDataBufferAllocatingTests.java
@@ -164,26 +164,29 @@ public abstract class AbstractDataBufferAllocatingTests {
 	@SuppressWarnings("deprecation") // PooledByteBufAllocator no longer supports tinyCacheSize.
 	public static Stream<Arguments> dataBufferFactories() {
 		return Stream.of(
-//			arguments(named("NettyDataBufferFactory - UnpooledByteBufAllocator - preferDirect = true",
-//					new NettyDataBufferFactory(new UnpooledByteBufAllocator(true)))),
+			// Netty 4
+			arguments(named("NettyDataBufferFactory - UnpooledByteBufAllocator - preferDirect = true",
+					new NettyDataBufferFactory(new UnpooledByteBufAllocator(true)))),
 			arguments(named("NettyDataBufferFactory - UnpooledByteBufAllocator - preferDirect = false",
 					new NettyDataBufferFactory(new UnpooledByteBufAllocator(false)))),
 			// 1) Disable caching for reliable leak detection, see https://github.com/netty/netty/issues/5275
 			// 2) maxOrder is 4 (vs default 11) but can be increased if necessary
-//			arguments(named("NettyDataBufferFactory - PooledByteBufAllocator - preferDirect = true",
-//					new NettyDataBufferFactory(new PooledByteBufAllocator(true, 1, 1, 4096, 4, 0, 0, 0, true)))),
-//			arguments(named("NettyDataBufferFactory - PooledByteBufAllocator - preferDirect = false",
-//					new NettyDataBufferFactory(new PooledByteBufAllocator(false, 1, 1, 4096, 4, 0, 0, 0, true)))),
+			arguments(named("NettyDataBufferFactory - PooledByteBufAllocator - preferDirect = true",
+					new NettyDataBufferFactory(new PooledByteBufAllocator(true, 1, 1, 4096, 4, 0, 0, 0, true)))),
+			arguments(named("NettyDataBufferFactory - PooledByteBufAllocator - preferDirect = false",
+					new NettyDataBufferFactory(new PooledByteBufAllocator(false, 1, 1, 4096, 4, 0, 0, 0, true)))),
+			// Netty 5
 			arguments(named("Netty5DataBufferFactory - BufferAllocator.onHeapUnpooled()",
 					new Netty5DataBufferFactory(BufferAllocator.onHeapUnpooled()))),
-//			arguments(named("Netty5DataBufferFactory - BufferAllocator.offHeapUnpooled()",
-//					new Netty5DataBufferFactory(BufferAllocator.offHeapUnpooled()))),
-//			arguments(named("Netty5DataBufferFactory - BufferAllocator.onHeapPooled()",
-//					new Netty5DataBufferFactory(BufferAllocator.onHeapPooled()))),
-//			arguments(named("Netty5DataBufferFactory - BufferAllocator.offHeapPooled()",
-//					new Netty5DataBufferFactory(BufferAllocator.offHeapPooled()))),
-//			arguments(named("DefaultDataBufferFactory - preferDirect = true",
-//					new DefaultDataBufferFactory(true))),
+			arguments(named("Netty5DataBufferFactory - BufferAllocator.offHeapUnpooled()",
+					new Netty5DataBufferFactory(BufferAllocator.offHeapUnpooled()))),
+			arguments(named("Netty5DataBufferFactory - BufferAllocator.onHeapPooled()",
+					new Netty5DataBufferFactory(BufferAllocator.onHeapPooled()))),
+			arguments(named("Netty5DataBufferFactory - BufferAllocator.offHeapPooled()",
+					new Netty5DataBufferFactory(BufferAllocator.offHeapPooled()))),
+			// Default
+			arguments(named("DefaultDataBufferFactory - preferDirect = true",
+					new DefaultDataBufferFactory(true))),
 			arguments(named("DefaultDataBufferFactory - preferDirect = false",
 					new DefaultDataBufferFactory(false)))
 		);